Many people on /vp/ will argue and bitch about which Pokemon game sold the best and was the most popular down to semantics and bias and sales numbers but few actually take into account install base. This chart takes care of that to show what percentage of system owners also had which Pokemon games.

From these figures, we can see the top five best selling Pokemon games are:
>1. Red and Blue with 31,050,000 sales
>2. Gold and Silver with 23,730,000 sales
>3. Sword and Shield with 20,350,000 sales
>4. Diamond and Pearl with 17,670,000 sales
>5. X and Y with 16,490,000 sales

However, some may argue these figures are skewed as more people owned Nintendo Switches than 3DSs, or more GameBoys than GameBoy Advances, and those people would be correct. Adjusting for game sales and calculating the percentages to find the install base, the top five Pokemon games with the highest install base are:
>1. Red and Blue with 26.16%
>2. Sword and Shield with 25.47%
>3. X and Y with 21.71%
>4. Sun and Moon with 21.33%
>5. Gold and Silver with 19.99%

The least popular Pokemon game being Pokemon Platinum, where only 4.93% of Nintendo DS owners also owned Platinum.